K30 build, frame clean up

Pusher · 2026-09-10T15:26:32-0400

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The engine support cross member is hard to see, but it's gray as well. I read it's something of a rarity, but I don't know.

83K31003 · 2026-09-10T18:36:51-0400

So is it just the finish coating color or is there any physical stamping difference on these items - first I’ve ever heard of this ?

I wish there was more details made public upon parts, or part type, differences from each assembly plant or dates of introductions or change overs when they started a running model year production change.

Pusher · 2026-09-10T19:31:47-0400

It's just certain parts, but the gray is the top coat. I had heard from other owners that it was limited to Janesville, but if I recollect, mine is a Flint truck also. There was a discussion on it, I'll try to find it.

Pusher · 2026-09-10T19:44:26-0400

https://www.gmsquarebody.com/threads/original-color-of-inner-wheel-wells-and-core-support.49116/

I forgot, the wheelhouses are gray also.

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I just remembered, my front anchor hangers were gray too, This pic is after I painted them. Anyway, the spring hangers were 3.75" inside width.

Pusher · 2026-09-10T19:52:52-0400

Here's some AI slop;

In the GM enthusiast community, "Janesville Gray" refers to a well-known factory assembly quirk found on classic 1973–1987 Chevy/GMC "Squarebody" trucks built at the GM Janesville Assembly plant in Wisconsin. [1]
While standard GM factory specifications across most assembly plants (like Flint or St. Louis) called for a semi-gloss black finish on hidden structural areas, the Janesville plant frequently deviated from this norm: [1, 2]

- Inner Wheel Wells & Core Supports: While conventionally black, a notable number of original trucks rolling off the Janesville line featured a distinct gray e-coat or gray primer/paint finish on the inner fenders and core support structures. [1]
- Factory Wheels: Enthusiasts restoring original trucks often note that Janesville-produced squarebodies came with a distinct gray or argent silver finish applied to the back and barrel of the factory steel wheels. [1]

Because of these variations, a gray underhood layout or gray wheel backing is a common indicator used by truck collectors to verify if a Squarebody was originally assembled at the Janesville facility. [1]

Pusher · 2026-09-10T19:57:38-0400

Maybe some chassis from Janesville went to Flint for final assembly? I don't know.

Pusher · 2026-09-10T20:12:27-0400

aasleson said:
Welcome! X2 on the rust not looking bad enough to be worried about. The wallered out mount bolt needs to be addressed though. I just did the same on my cucv, 31 gallon burb tank and the 2 inch ORD shackle flip

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This is exactly what I'm thinking, thank you.

83K31003 · 2026-09-10T20:20:56-0400

I’ve noticed the gray-ish paint on certain trucks over the years, such as core supports and inner fender wells, but just assumed that they were wrecked at some point and the body shop didn’t paint them correctly - good to know !

Appreciate the info.

K30 build, frame clean up

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